[Shop-talk] installing a helicoil

[gerrybraz at cablespeed.com (Gerald Brazil)]

John, I'd take it to a professional machine shop. The real secret to getting
an accurately fitted Helicoil is holding the work securely and having drill
and tap exactly vertical. It is probably best done on a milling machine. A
machine shop will do it right, you probably have a 60/40 chance.....If you
screw it up you not only have the cost of a Helicoil kit but the cost of a
new head. 

FWIW